Aspects on the variation of certain physical-chemical indices during must alcoholic fermentation

Abstract

The paper presented data concerning the variation of physical-chemical indices during must alcoholic fermentation: DM – soluble dry matter, pH – real acidity, ITP – index of total polyphenols, χ–conductivity, TDS – total dissolved substances, Eh–redox potential, rH– index of Eh quantification. In relation to the values of these indices, we have investigated the evolution of main composition characteristics, respectively reducing sugars, alcohol, total acidity, volatile acidity and total phenolic compounds. The experiments have been conducted on two musts obtained from white varieties (Muscat Ottonel and Sauvignon) from the Vine Growing Centre of Copou-Iaşi and on marc obtained from two red varieties (Fetească neagră and Băbească neagră), from the Vine Growing Centre of Uricani, Iaşi vineyard, vintage of year 2006. White musts were obtained by grape crushing, removal of berries from cluster and by pressing the marc resulted at primary grape processing. Marc obtained from black varieties has been submitted to maceration-fermentation for 120 h, then the must-wine mixture continued its fermentation until sugar finishing. Determinations have pointed out a variation in time of the values of studied indices, according to the oenological potential of each variety and the used technology. According to these variations of the values of studied indices, one may find that after a certain period of time (72 hours), a change took place in the equilibrium condition of the compounds formed during the fermentation process, especially of those involved in the insolubilization of tartaric salts; this aspect was also supported by the evolution of the values of conductivity, of redox potential and TDS, especially in white wines.